Fracturing apparatus



Oct. 21, 1989 R. wom 8,473,714

FRACTURING '"APPARATUS Filed D60. 14, 1967 INVENTOR. Roberf Woody z a o BY 55 5 w AGENT United States Patent O 3,473,714 FRACTURQG APPARATUS Robert Woody, Bay City, Mich., assignor to 'Ihel Dow Chemical Company, Midland, Mieli., a corporatlon of Delaware Filed Dec. 14, 1967, Ser. NO. 690,540

rm. C1. Bzsf 3/00 `IJ.S. Cl. 225-97 Clalms ABSTRACT OF THE DISCLOSURE Brittle strands are fractured to form pellets employing a pair of opposed rolls which 'are hollow and have a plurality of inserted teeth formed from flat strips, the strips being generally radially oriented and beneficially resiliently retained. The roll is generally self-cleaning.

This invention relates to fracturing apparatus, and more particularly relates to an improved form of fracturing apparatus adapted to transform brittle strandular material into a plurality of pellets.

Beneficially, many brittle materials are desirably handled in the form of pellets, the pellets being prepared from strands of the brittle material. One of such brittle materials is polystyrene which frequently is extruded as a strand of a convenient cross-sectional configuration and size; the strand is subsequently broken to form a plurality of pellets. A shearing action applied to such a brittle strand frequently results in undesirable pellets. Oftentimes the pellets have multiple fractures at the end portions, and frequently particles of widely varying size are obtained which vgive rise to undesirable dust, moisture absorption and the like. A significant and substantial improvement in the fracturing of brittle strands is the fracturing of the strand by exing the strand rather than subjecting the strand to shear or impact means. By fiexing the strand until it breaks, relatively clean fractures and uniform size pellets are obtained. A particularly advantageous manner of accomplishing this is to feed the strand between a pair of toothed drums or gears wherein opposing teeth of the opposing drums are spaced apart from each other and the strand is bent until it ruptures. One mode of such an embodiment is the situation where the strand is supported by two teeth of one drum and pressed against one tooth of the opposing drum which is positioned midway between the two teeth, thereby fiexing the strand in such a manner that it ruptures and forms two pellets, each pellet having a length of about one half of the distance between the terminal ends of the teeth remote from the drum. In certain instances, difiiculty is encountered if the strands being fractured require sufiicient bending that they are forced into the space between adjacent teeth and become lodged, or on occasion, the nature of the material may be such that it tends to adhere to the drum and be retained in the spaces between the teeth, such as in the case of polystyrene strands having a minor amount of water on the surface. Desirably, such an apparatus should be self-Cleaning and provide little or no means for pellets to be retained by the roll or gear configuration in a manner which might interfere with future fracturing operations.

It would be desirable if there were available an improved fracturin g means for brittle strands.

It would also be desirable if there were available an improved fracturing drum or assembly from which particles or pellets are readily released.

It would also be desirable if such an improved apparatus were of relatively simple construction and readily repaired.

ICC

These benefits and other advantages in accordance with the present invention are achieved in a fracturing roll, the fracturing roll comprising a mandrel adapted to rotate about an axis of rotation, the mandrel having affixed thereto at least a first fiange and a second fiange in spaced apart relationship and defining a space therebetween, the first and second flanges having terminal edges disposed remotely from the axis of generation, the flanges defining a plurality of slots in spaced relationship about the periphery thereof, each of the slots being substantially equally spaced from the 'axis of rotation and extending generally parallel thereto, each slot in the first fiange having an equivalent slot in the second fiange and a line joining a slot of the first fiange and its equivalent slot in the second fiange in generally parallel relationship to the axis of rotation, a plurality of elongate members, each of the elongate members having first and second major surfaces and first and second edges, the elongate members being resiliently retained within the slots and the elongate members extending in a direction generally parallel to the axis of rotation.

Further features and advantages of the present invention will become more apparent from the following specification taken in connection with the drawing wheren:

FIGURE 1 is a schematic representation of an apparatus in accordance with the invention.

FIGURE 2 is a schematic sectional view of a fracturing roll in accordance with the invention.

FIGURE 3 is a fractional end view of the roll of FIG- URE 2.

In FIGURE 1 there is schematically depicted a strand fracturing apparatus generally designated by the reference numeral 10. The apparatus 10 comprises in cooperative combination a strand supply means 11. A plurality of strands 12 are provided by the strand supply means 11. A fracturing assembly 14 is disposed generally adjacent the strand supply means 10. The fracturing assembly 14 comprises a support and drive means 15, a first fracturing roll 16 and a second fracturing roll 17. The fracturing rolls 16 and 17 are supported on shafts 18 and 19, respectively, and rotated in the direction indicated by the arrows, whereby strands 12 are withdrawn from the source 11. The roll 16 has disposed on the cylindrical surface thereof a plurality of elongate spaced apart members 16a. A similar plurality of elongate spaced apart members 17a are disposed on the cylindrical surface 17. The rolls 16 and 17 are driven and synchronized by the means 15 in such a manner that the elongate members 16a and 17a are maintained in spaced apart relationship; and at the point on the roll surfaces where the rolls approach each other most closely, the teeth of one roll 'project toward a space between the elongate members of the other roll. The elongate members cooperate with each other to flex and fracture the strand 12 and provide a plurality of pellets 20. A source of compressed gas 21 delivers a rapidly moving stream of gas to each of the rolls 16 and 17 In FIGURE 2 there is depicted an elongate sectional view of a roll generally designated by the reference numeral 25. The roll 25 is equivalent to the rolls 16 and 17 schematically depicted in FIGURE 1. The roll 25 comprises a hollow mandrel or support 26 carried by a rotating means or shaft 27 having an axis of rotation 28. The mandrel 26 defines first, second, third and fourth radially extending fianges 30, 31, 32 and 33, respectively. A generally annular space 35 is defined between the adjacent flanges 30 and 31; a second annular space 36 is defined between the fianges 31 and 32, and a third annular space 37 is defined between the flanges 32 and 33. The first fiange 30 defines a plurality of radially disposed outwardly facing slots 30a which are disposed in angular relationship to each other about the peripheral edge of the fiange 30. Corresponding slots 31a, 32a and 33a are defined by the flanges 31, 32 and 33, respectively. Each of the flanges 30, 31, 32 and 33 have a plurality of openings 30b, 31b, 32b and 33b defined therein. The openings 30b, 31b, 32h and 33B 'provide communication between the spaces 35, 36 and 37 and space external to the roll. A plurality of elongate elements 39 are disposed peripherally about the roll and are disposed within the slots 30a, 31a, 32a and 33a. Each of the elongate elements have a first outwardly facing edge 41, a first major face 42, a second or inwardly facing edge 43 and a second major face 44. The elongate elements 39 have the major faces 42 and 44 lying generally in a plane containing the axis of rotation 28. A first resilient retaining means 46 engages one end of the elongate elements 39 and resiliently urges them into the slots 30a. A second resilient retaining means 47 engages the opposite ends of the elements 39 and resiliently urges the elements into ythe slot 33a of the flange 33. A spring wire formed into a circular configuration having overlapping unconnected ends is suitable for such a retaining means. The resilient retaining means 46 and 47 serve to maintain the elongate elements in a desired position when radially inward force is exerted on the first edge 41 and permit movement of Ithe elongate member radially inwardly when a force is applied to the second edge 43 in a radially outwardly direction. An element displacing means 48 is dsposed generally adjacent the first flange 30. The element displacing means comprises a support 49 having adjustably aflixed thereto an adjustable bearing 51, a shaft 52 generally parallel to the shaft 27 and a roll or element engaging means 53. The roll 53 is adapted to engage a portion of the second edge 43 of the elongate elements 39 and dsplace them radially outwardly from the slots 30a, 30b and 30a, thereby increasing spacing between adjacent elongate members 39. As the roll 25 is rotated, the roll 53 successively engages elongatemembers 39 and displaces them radially outwardly.

FIGURE 3 depicts a schematic fractional end View of a portion of the flange 33 showing the location of the slots 33a and 'a plurality of elongate elements 39 disposed therein.

In operation of -the apparatus of the present invention, a pair of rolls such as the rolls 25 are employed in an apparatus such as is depicted in FIGURE 1. As the rolls rotate, strands such as the strands 12 'are engaged by the outer or first edges 41 of the elongate elements and flexed to a degree suficient to fracture the elements into particles. One mode of fracture of strands is the support of a strand by two of the elements on one roll while pressure is applied to the strand by one of the elements of the other roll at a location about midway `'between the support points. If for any reason, the particles drop into one or more of the spaces 35, 36 and 37, tumbling action tends to discharge the particles through the openings 30b and 33b while the openings 31h and 3217 permit flow of particles within the roll toward openngs 30h and 33b, respectively. If desired, a stream of gas, such as a stream of compressed air, may be directed into one or more of the openings such as the openings 30b or 33b to cause gas entrainment of the particles and discharge them from the opposite end of the roll from which the gas stream is applied.

If the material being fractured results in granules which are not readily free flowing or the granules tend to stick to each other or to the roll, a fracturing element displacing device such as the device 48 is beneficially applied to a portion of the roll wherein by displacing elongate elements, the spacing between the elements is increased and entrapped particles are released.

Apparatus generally as depicted in FIGURE 1 employing rolls as depicted in FIGURES 2 and 3 are used with great benefit for fracturing of brittle Synthetic resinous materials such as polystyrene and brittle styrenetype polymers.

As is apparent from the foregoing specification, the present nvention is susceptible of being embodied with various alterations and modifications which may ditfer particularly from those that have been described in the preceding specification and description. For this reason. it is to be fully understood that all of the foregoing is intended to be 'merely illustrative and is not to be construed or interpreted as being restrictve or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto-appended claims.

What is claimed is:

1. A roll particularly suited and adapted for the fracturing of brittle strands, the fracturing roll comprising a mandrel adapted to rotate about an axis of rotation.

the mandrel having afiixed thereto at least a second flange in spaced apart relationship and defining a space therebetween, the

having terminal edges disposed remotely from the axis of generation, the flanges defining a plurality of slots in spaced relationship about the periphery thereof, each of the slots being substantially equally spaced from the axis of rotation and extending generally parallel thereto, each slot in the first flange having an equivalent slot in the second flange and a line joining the slot of the first flange and its equivalent slot in the second flange being generally parallel to the axis of rotation,

a plurality of elongate members, each of the elongate members having first and second major surfaces, and first and second edges, the elongate members beng resiliently retained within the slots and the elongate members extending in a direction generally parallel to the axis of rotation.

2. The roll of claim 1 wherein the first and second flanges each define at least one opening therethrough commnnicating with the space lbetween the 'flanges and space external to the roll. i

3. The roll of claim 1 wherein resilient retaining means in engagement with the elongate members are disposed adjacent the first flange and the second flange.

4. 'The roll of claim 1 wherein theelongate elements are disposed with the first edges remotely disposed from the longitudinal axis and the second edge generally adjacent the longitudinal axis.

5. The roll of claim 1 including a third flange disposed between the first and second flanges, the third flange defining a plurality of elongate member-engagng slots.

6. The roll of claim 1 in operative combination with a like roll, means rotatably support the rolls in opposed parallel spaced apart relationship.

7. The roll of claim '6 including Va strand supply means.

8. The roll of claim 7 including means to sequentially dsplace at least a portion of the elongate members generally radially outward from the axis of rotation as the roll is rotated.

9. The roll of claim 8 wherein the displacing means comprises a displacing roll in operative engagementwith a portion of a radially inwardly positioned second edge of the elongate elements and disposed adjacent the first flange.

10. The roll of claim 6 including means to supply a stream of gas directed at said roll.

first and second flanges References Cited UNITED STATES PATENTS 2,101,7oo 12/1937 chesmut 22s 1o4x 3,317,1oo 5/1967 Flemmingaal. 225-197 JAMES M. MEISTER, Primary Examiner 

